A belt retractor having the general characteristics mentioned above has been described in DE 195 39 619 C2. The locking lever is connected to the sensor mass on the end facing away from the engaging tip in a form-fitting manner and forming a support. The form fit occurs in an extension of the sensor mass which protrudes downwardly through a hole in the contact surface of the holder part.
The problem with such generic belt retractors of the type described above is that in case of major vibrations, e.g. when dropping the belt retractor or when upholstering seats, the sensor lever can be bent with respect to the holder part and to the sensor mass, so that it subsequently no longer complies with the high demands regarding engagement accuracy. Another known problem of belt retractors is that the sensor mass and/or the locking lever carry out relative movements which result in an unwanted noise (buzz, squeak, rettle) in the belt retractor.
The underlying object of the invention therefore is to provide a belt retractor in which the problems mentioned above are prevented.
This object is attained by means of the characteristics of the belt retractor described herein.
The basic concept of the invention is that a projection protruding into the hole is provided at the border of the hole facing the locking lever, against which the locking lever contacts on deflection in one direction. The contact surface of the locking lever on the holder part is enlarged by the proposed projection, and the lever arms, by means of which the locking lever contacts the holder part, are reduced. Owing to the enlarged contact surface and the reduced lever arms, the maximum stress on the locking lever and the associated probability of a deformation of the locking lever during the vibrations or handling of the belt retractor or any other stress on the locking lever is reduced.
Furthermore, the enlarged contact surface, the positional accuracy of the locking lever, of the holder part and of the sensor mass relative to one another are in general improved, which is advantageous for the accuracy of the response threshold of the sensor as well as with regard to the prevention of an unwanted blocking of the belt retractor when the belt retractor is assembled. Another advantage resulting from the invention is that the relative movements of the sensor lever with respect to the holder part and to the sensor mass are limited by the provided projection and the noise in the belt retractor is thus reduced.
It is further proposed that the projection is formed as a tongue projecting into the hole which substantially extends in the longitudinal direction of the locking lever. As a result of the proposed shape of the projection, the lever arm acting between the holder part and the locking lever is significantly reduced, where the lever arm can at the same time be configured to be resilient because of the tongue-shaped projection, so that the stop of the locking lever at the holder part can accordingly be configured to be soft.
It is also proposed that the thickness of the projection decreases toward its free end. Owing to the decreased thickness of the projection, the stress on the locking lever is very low at the start of the contact, so that it cannot, or can only minimally be stressed in case of minor deflections. The spring rigidity of the projection increases with the increasing deflection of the locking lever, so that a correspondingly increased counteracting force is opposed to the deflection of the locking lever.
Another preferred embodiment of the invention is that the locking lever contacts the holder part via a noise-reducing insulating layer. Such an insulating layer can, for example, be realized by means of a soft plastic material, in particular by means of an elastomeric layer. The insulating layer can be arranged at the projection and/or at the contact surface of the locking lever that contacts the projection. What is important is that the insulating layer reduces the noise occurring on contact of both parts.
It is further proposed that a projection be provided at the sensor mass and/or on the holder part for the alignment of the sensor mass in a predefined position and which engages in a recess provided on the other part, respectively. The projection allows for the reliable arrangement of the sensor mass in a predefined alignment on the holder part by means of an automated mounting process, and consequently for the reduction of the error probability of the sensor as a result of a misaligned sensor mass.
In this case, at least one second projection can be provided at the sensor mass and/or on the holder part which engages in another second recess provided on the other part. The probability for the sensor mass to twist under the effect of an impulse is reduced by the second projection, so that the sensor carries out its function even in case of strong vibrations.
The projections should further have a tapered, preferentially triangular cross-sectional surface in the areas engaging in the recesses, as a result of which the sensor mass can swivel in the recesses. It is thus ensured that the sensor mass is kept in the predefined alignment by the projections but without obstructing the swiveling movement.